1. Technical Field
The present invention relates to an organic light emitting diode (OLED) display device, and more particularly, to an OLED display device including four color emitting layers and method of fabricating the OLED display device.
2. Related Art
An OLED display device of new flat panel display devices is a self-emitting type. Since the OLED display device does not require a backlight, which is required for a liquid crystal display device, the OLED device has a thin profile and light weight.
Particularly, various colors, e.g., red, green, blue, cyan, light-blue, and so on, can be displayed using an organic material. The red and green phosphorescent materials having excellent efficiency and lifetime are used, while the deep-blue fluorescent material having similar color property and lifetime as the red and green phosphorescent materials are used. However, the deep-blue fluorescent material has low efficiency such that there is a disadvantage in power consumption.
FIG. 1 is a graph of simulation data for showing power consumption in an OLED display device using a red phosphorescent material PH_R, a green fluorescent material FL_G, a green phosphorescent material PH_G, a blue phosphorescent material PH_B1 and a blue fluorescent material FL_B2.
FIG. 1 shows power consumption of the OLED display device, which uses the red phosphorescent material PH_R, the green phosphorescent material PH_G and the blue phosphorescent material PH_B1, is decreased by about 45% in comparison to the OLED, which uses the red phosphorescent material PH_R, the green phosphorescent material PH_G and the blue fluorescent material FL_B2.
FIG. 2 is a schematic plane view of the sub-pixel arrangement in the related art OLED device.
In FIG. 2, one pixel 100a includes red, green and blue sub-pixels R, G and B. On the other hand, another pixel 100b includes the red sub-pixel R, the green sub-pixel G, a light-blue sub-pixel B1 of a phosphorescent material and a deep-blue sub-pixel B2 of the fluorescent material to prevent a problem of power consumption increase resulted from the fluorescent material.
In addition, to display images, the light-blue material is used above 70%, and the deep-blue material is used below 30%. The light-blue image is displayed using the phosphorescent material, while the deep-blue is displayed using the fluorescent material. Accordingly, the four emitting materials and four deposition processes are required to fabricate the OLED display device having the pixel 100b. 
Referring to FIG. 3, which is a schematic cross-sectional view of the related art OLED display device including red, green, first blue and second blue sub-pixels, a fabricating process of the OLED display device is explained.
As shown in FIG. 3, the OLED display device includes an organic emitting cell. The organic emitting cell includes a first electrode 106 connected to a thin film transistor (TFT) T, which is formed on a substrate 101, a hole injecting layer 107, a hole transporting layer 108, an emitting layer 109, an electron transporting layer 110, an electron injecting layer 111, and a second electrode 112. The hole injecting layer 107, the hole transporting layer 108, the emitting layer 109, the electron transporting layer 110, the electron injecting layer 111, and the second electrode 112 are stacked on the first electrode 106.
Particularly, after forming the TFT T on the substrate 101, the first electrode 106, the hole injecting layer 107 and the hole transporting layer 108 are formed. Next, the red emitting layer 109R, the green emitting layer 109G, the light-blue emitting layer 109B1 and the deep-blue emitting layer 109B2 are formed in the red sub-pixel R, the green sub-pixel G, the first blue sub-pixel B1 and the second blue sub-pixel B2. To form the four-colored pixel structure, a step of forming the light-blue emitting layer 109B1 or the deep-blue emitting layer 109B2 is further required.
Namely, since the OLED display device having the four-colored pixel structure includes the red, green, first blue and second blue sub-pixels R, G, B1 and B2, production costs and fabricating steps are increased in comparison to the OLED display device having the three-colored pixel structure. In addition, since the fluorescent material is used for displaying the deep-blue, there are still disadvantages in power consumption.